Biology Chapter: Metabolism and Enzymes
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Questions and Answers

What happens to a molecule when it loses electrons?

  • It becomes reduced
  • It forms a new chemical bond
  • It generates a negatively-charged ion
  • It becomes oxidized (correct)

    • Which of the following statements is true regarding oxidation and reduction?

  • Reduction is the breaking of a chemical bond
  • Oxidation generates a positively-charged ion (correct)
  • Oxidation always involves gaining electrons
  • Reduction results in a positively-charged ion

    • In the process of cellular respiration, what is the ultimate fate of energy-poor electrons?

  • They are stored as fats
  • They are given to oxygen (correct)
  • They are given to carbon dioxide
  • They are converted into glucose

    • What is the first step of glycolysis in converting glucose into ATP?

    <p>Oxidation of glucose</p> Signup and view all the answers

    Which statement correctly describes the roles of NAD+ and NADH in oxidation and reduction?

    <p>NAD+ is the reduced form of the molecule</p> Signup and view all the answers

    What is the primary reason humans need to eat?

    <p>To provide energy and building blocks for growth and maintenance</p> Signup and view all the answers

    What role do chemical bonds play in metabolism?

    <p>They store and release energy during metabolic reactions</p> Signup and view all the answers

    What is a defining feature of ATP that makes it effective for energy storage?

    <p>It has high-energy phosphate bonds</p> Signup and view all the answers

    What happens during catabolic reactions?

    <p>Molecules are broken down, releasing energy</p> Signup and view all the answers

    During which process is a proton gradient built across the inner mitochondrial membrane?

    <p>Electron Transport Chain</p> Signup and view all the answers

    In cellular respiration, what is the function of electron carriers?

    <p>To transport electrons and facilitate their energy transfer</p> Signup and view all the answers

    What is formed during alcohol fermentation?

    <p>Ethanol and carbon dioxide</p> Signup and view all the answers

    How does feedback inhibition regulate cellular respiration?

    <p>By slowing down enzyme activity when products accumulate</p> Signup and view all the answers

    What is the primary role of food in energy metabolism?

    <p>To store energy in their chemical bonds</p> Signup and view all the answers

    Which of the following correctly describes catabolic reactions?

    <p>They break down large polymers into smaller monomers.</p> Signup and view all the answers

    What distinguishes endergonic reactions from exergonic reactions?

    <p>Endergonic reactions require energy.</p> Signup and view all the answers

    What is metabolism?

    <p>The sum of all the chemical reactions in cells.</p> Signup and view all the answers

    How do enzymes affect chemical reactions in metabolism?

    <p>They speed up the rate of chemical reactions.</p> Signup and view all the answers

    What happens to the energy in exergonic reactions?

    <p>It is released into the environment.</p> Signup and view all the answers

    The products of catabolic reactions are primarily used for which type of reaction?

    <p>Anabolic reactions</p> Signup and view all the answers

    Which of the following statements about anabolic reactions is correct?

    <p>They build larger polymers from smaller monomers.</p> Signup and view all the answers

    What is the initial molecule that starts the Citric Acid Cycle?

    <p>Oxaloacetate</p> Signup and view all the answers

    How many carbon dioxide molecules are released during the Citric Acid Cycle starting from 2 acetyl CoA?

    <p>4</p> Signup and view all the answers

    Which molecules are primarily produced as a result of the Citric Acid Cycle?

    <p>ATPs and NADH</p> Signup and view all the answers

    What is the role of oxidative phosphorylation in cellular respiration?

    <p>To generate the most ATP</p> Signup and view all the answers

    What happens to the energy stored in electron carriers during cellular respiration?

    <p>It is transformed into ATP</p> Signup and view all the answers

    Which component of the mitochondria does the Electron Transport Chain create a concentration gradient across?

    <p>Inner mitochondrial membrane</p> Signup and view all the answers

    What is released from pyruvate during its oxidation before entering the Citric Acid Cycle?

    <p>Acetyl CoA</p> Signup and view all the answers

    How many NADH molecules are generated through glycolysis, pyruvate oxidation, and the Citric Acid Cycle combined?

    <p>10</p> Signup and view all the answers

    What is the primary purpose of oxidative phosphorylation in cellular respiration?

    <p>To harness energy from electron carriers to produce ATP</p> Signup and view all the answers

    Which stage of cellular respiration occurs in the presence of oxygen?

    <p>Citric Acid Cycle</p> Signup and view all the answers

    What role does oxygen play in the electron transport chain (ETC)?

    <p>Oxygen accepts low-energy electrons to facilitate the flow of new electrons</p> Signup and view all the answers

    What is the critical outcome of fermentation in cells lacking oxygen?

    <p>Renewal of NAD+ to sustain glycolysis</p> Signup and view all the answers

    What molecule is produced during alcoholic fermentation?

    <p>Ethanol</p> Signup and view all the answers

    How does feedback inhibition regulate cellular respiration?

    <p>High levels of end products inhibit the pathways leading to their formation</p> Signup and view all the answers

    Which of the following processes generates lactic acid?

    <p>Lactic Acid Fermentation</p> Signup and view all the answers

    What happens to NADH in the electron transport chain?

    <p>It donates electrons and is oxidized to NAD+</p> Signup and view all the answers

    What is the metabolic fate of pyruvate in the absence of oxygen?

    <p>It is converted into ethanol or lactic acid</p> Signup and view all the answers

    What is the effect of high ATP concentration on enzymes of cellular respiration?

    <p>Enzymes are inhibited from functioning</p> Signup and view all the answers

    Study Notes

    Why We Eat

    • The human body needs food for energy
    • Energy is vital for building macromolecules, such as proteins and nucleic acids
    • Energy is also required for life-sustaining processes, including active transport

    Metabolism: The sum of all chemical reactions in cells

    • Catabolic reactions break down large molecules into smaller monomers, releasing energy
    • Anabolic reactions build large molecules from smaller monomers, and require energy
    • Exergonic reactions release energy because products have less energy than reactants
    • Endergonic reactions require energy because products have more energy than reactants
    • Catabolic and anabolic reactions are connected, with monomers from catabolism used in anabolism
    • Exergonic and endergonic reactions are linked, with energy from exergonic reactions powering endergonic ones

    Enzymes: Catalysts for Life

    • Enzymes accelerate chemical reactions
    • Without enzymes, reactions would be too slow for life
    • Enzymes facilitate both anabolic and catabolic reactions
    • Enzymes act on substrates to generate products

    Oxidation and Reduction: The Transfer of Electrons

    • Breaking and building of chemical bonds involve electrons
    • Oxidation involves the loss of electrons, often seen as bond breaking
    • Oxidation can create a positively charged ion
    • Reduction involves the gain of electrons, often seen as bond building
    • Reduction can create a negatively charged ion

    Cellular Respiration: Energy from Glucose

    • Cellular respiration converts glucose into energy
    • Glucose oxidation releases energy stored in its chemical bonds
    • This energy is captured in the chemical bonds of ATP
    • Low-energy electrons are given to oxygen, reducing it

    ATP & ADP: The Energy Currency of Cells

    • ATP (adenosine triphosphate) is a high-energy molecule
    • The energy is stored in the bonds between phosphate groups
    • ATP is used by cells as an energy source by breaking those bonds
    • ADP (adenosine diphosphate) is a lower-energy molecule
    • ADP is formed when ATP loses a phosphate group

    Glycolysis: Splitting Glucose

    • Occurs in the cytoplasm
    • Starts with glucose (6 carbons)
    • Ends with 2 pyruvate (3 carbons each)
    • Generates 2 ATP and 2 NADH

    Pyruvate Oxidation: Preparing for the Citric Acid Cycle

    • Occurs in the mitochondrial matrix
    • Pyruvate is oxidized to acetyl CoA
    • Generates 1 NADH per pyruvate

    The Citric Acid Cycle (Krebs Cycle): Further Oxidation

    • Occurs in the mitochondrial matrix
    • Acetyl CoA enters the cycle, adding 2 carbons
    • Those 2 carbons are released as CO2
    • Generates 3 NADH, 1 FADH2, and 1 ATP per acetyl CoA

    Oxidative Phosphorylation: The Electron Transport Chain

    • Occurs in the inner mitochondrial membrane
    • Electron carriers (NADH and FADH2) donate electrons
    • Electrons move through a series of proteins, releasing energy
    • This energy is used to pump protons across the membrane, creating a gradient

    Chemiosmosis: Using the Proton Gradient

    • The proton gradient fuels ATP synthase
    • ATP synthase uses the energy from proton movement to generate ATP
    • This is the main source of ATP production during cellular respiration

    Oxygen's Crucial Role

    • Oxygen is the final electron acceptor in the ETC
    • It removes low-energy electrons, allowing new electrons to enter
    • Without oxygen, the ETC stops, halting ATP production

    Fermentation: Anaerobic ATP Production

    • Fermentation occurs when oxygen is absent
    • The goal is to regenerate NAD+ so glycolysis can continue
    • Without NAD+, glycolysis can't generate any ATP

    Alcohol Fermentation

    • Used by yeast
    • Pyruvate is converted to ethanol
    • NADH is oxidized to NAD+

    Lactic Acid Fermentation

    • Used by bacteria, fungi, and mammals
    • Pyruvate is converted to lactic acid
    • NADH is oxidized to NAD+

    Regulation of Cellular Respiration: Feedback Inhibition

    • Cellular respiration is regulated by feedback inhibition
    • Products of reactions can inhibit their own production
    • Enzymes involved in respiration are sensitive to ATP levels
    • High ATP levels inhibit enzyme activity
    • Low ATP levels stimulate enzyme activity

    Macromolecules Breakdown

    • Other macromolecules, like fats and proteins, can be catabolized
    • They use some of the same pathways as glucose breakdown

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    Description

    Explore the essential concepts of metabolism and enzymes in this quiz. Understand the significance of catabolic and anabolic reactions, as well as the role of enzymes as catalysts in living organisms. Test your knowledge on energy requirements and chemical reactions within cells.

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